Epoxy resin composition, process for producing fiber-reinforced composite materials and fiber-reinforced composite materials

ABSTRACT

The present invention relates to an epoxy resin composition consisting of components (a), (b) and (c) defined below, wherein the amount of component (c) based on 100 parts by weight of component (a) is 1 to 30 parts by weight; component (a) is liquid; and components (b) and (c) are homogeneously dissolved in component (a):  
     (a) epoxy resin,  
     (b) anionic polymerization initiator, and  
     (c) proton donor.  
     The present invention also relates to a process for producing fiber-reinforced composite material where a thermosetting resin composition is injected into reinforcing fiber substrates placed in a mold maintained at a specific temperature T m  between 60 to 180° C., and heated to cure in a mold at T m , such that the following conditions (7) to (9) are satisfied:  
     t i ≦10  (7)  
     t m ≦60  (8)  
     1&lt;≦ t   m   /t   i ≦6.0  (9)  
     wherein,  
     t i  is time from the beginning of injection to the termination of injection (min.), and  
     t m  is time from the beginning of injection to the beginning of the demolding (min.)  
     The present invention produces high Vf fiber-reinforced composite materials with good productivity.

FIELD OF THE INVENTION

[0001] The present invention relates to an epoxy resin composition thatis preferably used for fiber-reinforced composite materials, and furtherrelates to a process for producing fiber-reinforced composite materialsby impregnating a reinforcing fiber substrate placed in a mold with aliquid thermosetting resin composition, and heating to cure, and furtherrelates to the fiber-reinforced composite materials made thereby.

BACKGROUND OF THE INVENTION

[0002] The use of fiber-reinforced composite materials consisting ofreinforcing fibers and matrix resins has been widely extended to thefields including aerospace, sports, and general industry fields, becausefiber-reinforced composite materials make it possible to designmaterials that have benefits of both reinforcing fibers and matrixresins.

[0003] As reinforcing fibers, glass fibers, aramid fibers, carbonfibers, boron fibers, and the like may be used. As matrix resins, boththermosetting resins and thermoplastic resins may be used, butthermosetting resins are more frequently used because reinforcing fiberscan be more easily impregnated the thermosetting resins. Asthermosetting resins, epoxy resins, unsaturated polyester resins, vinylester resins, phenolic resins, maleimide resins, cyanate resins, and thelike may be used.

[0004] For producing fiber-reinforced composite materials, variousmethods such as prepreg method, hand lay-up method, filament windingmethod, pultrusion method, RTM (Resin Transfer Molding) method, and thelike may be used.

[0005] Among them, the RTM method where a reinforcing fiber substrateplaced in a mold is impregnated with a liquid thermosetting resin, andheated to cure has a great advantage that a fiber reinforced compositematerials of complicated shape can be molded.

[0006] Recently, there has been a need for producing fiber-reinforcedcomposite materials of high fiber volume fraction (Vf) (particularlymore than about 45%), which are lightweight, and excellent in mechanicalproperties such as strength and elastic modulus, by using the RTMmethod. However, it has been difficult to efficiently producefiber-reinforced composite materials with high Vf in a short time periodusing the conventional RTM method.

[0007] In the RTM method, the packing fraction of reinforcing fibers ina mold should be high to produce fiber-reinforced composite materialswith high Vf, because the Vf of a product is mainly determined by thepacking fraction of reinforcing fibers in a mold. If the packingfraction is high, permeability is low, because high packing fractionmeans low void fraction. And if the permeability is low, injection timeof the resin composition is lengthened.

[0008] If the thermosetting resin composition is heated to cure at aconstant temperature, viscosity of the liquid composition increases, andthen, gelation occurs. After gelation, rubbery polymer is obtained. Theglass transition temperature of the polymer increases as the curingreaction progresses. If the glass transition temperature exceeds thecuring temperature, the polymer turns to a glassy polymer. In general,demolding is carried out after vitrification. For general thermosettingresin compositions, the ratio of the time required from the beginning ofinjection to vitrification to the time from the beginning of theinjection to a point during which the thermosetting resin compositionsmaintain liquid phase with a viscosity adequate for injection is usuallygreater than 6.

[0009] In cases of producing fiber-reinforced composite materials whoseVf is not high, it is possible to carry out the method in a short time(several minutes or about ten minutes), where injection is terminatedbefore the viscosity of the thermosetting resin compositions becomes toohigh, and curing for a predetermined time and demolding are carried outwhile maintaining the mold temperature constant, because injection timeof the resin composition can be short. This method is often called S-RIM(Structural Reactive Injection Molding).

[0010] However, in cases fiber-reinforced composite materials with highVf, it is impossible to carry out the same method mentioned above at themold temperature at which the curing reaction is terminated in a shorttime, because rapid increase of viscosity, and furthermore, gelationoccurs during impregnation. On the other hand, if the temperature or thereactivity of the thermosetting resin composition is lowered to preventrapid increase of viscosity during impregnation, the time before thedemolding is increased, and the overall molding process time isincreased. To decrease molding process time, raising the temperature ofthe mold is often used after the termination of injection. This method,however, is not sufficient to decrease total molding process timebecause the method requires additional time to raise and lower thetemperature of the mold.

[0011] The object of the present invention is to provide the epoxy resincompositions that have a low ratio of time required from the beginningof the injection to vitrification to time required from the beginning ofthe injection to a point during which the thermosetting resincompositions maintain liquid phase having viscosity adequate forinjection.

[0012] Epoxy resin compositions that are similar to those of the presentinvention are disclosed in Japanese patent laid-open publication No.1978-113000. These epoxy resin compositions comprise epoxy resins,imidazole derivatives, methanol and/or ethanol. In these epoxy resincompositions, methanol and/or ethanol function as solvent, and occupy alarge proportion of the compositions. The above patent document alsostates that methanol and (or) ethanol is volatilized before curing. Ifsuch epoxy resin compositions are injected into a mold and heated tocure, it is impossible to volatilize the methanol and/or ethanol. Ifcuring is carried out in the presence of large amounts of methanol and(or) ethanol, cured resin products with crosslinking structure cannot beobtained or cured resin products having very low crosslinking density isobtained. Therefore, these epoxy resin compositions have not been usedas a matrix resin for the RTM method.

[0013] Japanese patent laid-open publication No. 1990-103224 disclosesepoxy resin compositions comprising epoxy resins, an imidazolederivative, boric acid and mannitol. In the compositions disclosed bythe above patent, solid bodies prepared by grinding the mixture ofimidazole derivatives, boric acid and mannitol is used to blend with theepoxy resins. However, if the reinforcing fiber substrate is impregnatedwith such epoxy resin compositions, heterogeneity of the composition israised because the solid bodies hardly penetrate into bundles ofreinforcing fibers. Thus, curing of the resin compositions isinsufficient in some regions, and cured resin products having high glasstransition temperature cannot be obtained. Therefore, these epoxy resincompositions have not used as a matrix resin for the RTM method.

[0014] Journal of Applied Polymer Science, Vol. 30, pp. 531-536discloses a mixture comprising p-cresol glycidyl ether, an imidazolederivative, and isopropyl alcohol. However, if this mixture is reacted,the resulting product is a soft linear polymer without a crosslinkingstructure. Therefore, this mixture cannot satisfy requirements of highglass transition temperature and strength necessary for a matrix resinin a fiber-reinforced composite material.

[0015] None of the above compositions or mixtures can increase glasstransition temperature even when heated to induce reaction, and are notsuitable for advantages such as provided by the present invention whichare to decrease the ratio of time from the beginning of the injection tovitrification, to the time from the beginning of the injection to apoint during which the thermosetting resin compositions maintain liquidphase having viscosity adequate for injection.

DETAILED DESCRIPTION OF THE INVENTION

[0016] The epoxy resin composition of the present invention solves thestated problems in the art. The epoxy resin composition of the presentinvention consists of components (a), (b) and (c) defined below, whereinthe amount of component (c) based on 100 parts by weight of thecomponent (a) is 1 to 30 parts by weight, component (a) is liquid, andcomponents (b) and (c) are homogeneously dissolved in component (a).

[0017] (a) epoxy resin

[0018] (b) anionic polymerization initiator

[0019] (c) proton donor

[0020] A process for producing the fiber-reinforced composite materialsof the present invention that provides a solution to the afore-statedproblems, is described below.

[0021] The process for producing fiber-reinforced composite materialswhere a thermosetting resin composition is injected into reinforcingfiber substrates placed in a mold maintained at the specific temperatureT_(m) between 60 to 180° C., and heated to cure at the specifictemperature T_(m) in a manner that the following conditions (7) to (9)are satisfied:

t_(i)≦10  (7)

t_(m)≦60  (8)

1<t _(m) /t _(i)≦6.0  (9)

[0022] wherein,

[0023] t_(i): time from the beginning of the injection to thetermination of injection (min.)

[0024] t_(m): time from the beginning of the injection to the beginningof the demolding (min.)

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1. represents change of cure index versus time obtained bydielectric measurement of the epoxy resin composition of the presentinvention.

[0026]FIG. 2. is the illustration of top surface and cross section ofthe mold used for producing the fiber-reinforced composite materials ofthe present invention.

[0027]FIG. 3. is the illustration of top surface and cross section ofthe arrangement of reinforcing fiber substrate, peel ply and resindistribution medium used in a process for producing planarfiber-reinforced composite materials of the present invention.

[0028]FIG. 4. is the illustration of top surface and cross section ofthe arrangement of reinforcing fiber substrate and core used in aprocess for producing sandwich structure fiber-reinforced compositematerials of the present invention.

[0029] Reference number 1 represents a cavity of a mold, referencenumber 2 represents an upper mold, reference number 3 represents lowermold, reference number 4 represents an inlet, reference number 5represents an outlet, reference numbers 6 and 7 represent runners,reference numbers 8 and 9 represent film-gates, reference numbers 10 and15 represent reinforcing fiber substrates, reference number 11represents a peel ply, reference number 12 represents a resindistribution medium, reference number 13 represents a core, andreference number 14 represents a resin feeder groove.

BEST MODE FOR CARRYING OUT THE INVENTION

[0030] First, the epoxy resin composition of the present invention isdescribed.

[0031] The epoxy resin composition of the present invention consists ofcomponents (a), (b) and (c) defined below, wherein the amount of thecomponent (c) based on 100 parts by weight of the component of (a) is 1to 30 parts by weight, the component (a) is liquid, and components (b)and (c) are homogeneously dissolved in component (a).

[0032] (a) epoxy resin

[0033] (b) anionic polymerization initiator

[0034] (c) proton donor

[0035] The component (a) of the present invention is an epoxy resin. Anepoxy resin is defined herein as a compound which has a plurality ofepoxy groups in one molecule.

[0036] It is preferable that component (a) has one member selected fromthe group consisting of an aromatic ring, a cycloalkane ring, and acycloalkene ring, because the resulting cured resin products have goodheat resistance and good mechanical properties such as elastic modulus.As the cycloalkane ring, a cyclopentane ring, a cyclohexane ring, andthe like, are preferable, and a bicycloalkane ring and a tricycloalkanering, such as norbornane ring and a tricyclo [5.2.1.0^(2.6)] decane ringthat have a cyclopentane ring or a cyclohexane ring in their structures,are also preferable. As the cycloalkene ring, a cyclopentene ring and acyclohexene ring are preferable, and a bicycloalkene ring and atricycloalkene ring that have a cyclopentene ring or a cyclohexene ringin their structures are also preferable.

[0037] The viscosity of component (a) of the present invention at 25° C.is preferably 1 to 30,000 mP s, more preferably 1 to 20,000 mP s, andfurther preferably 1 to 10,000 mP s. If the viscosity is higher thanthese ranges, the initial viscosity of the epoxy resin composition atthe injection temperature of 60 to 180° C. may become high, so that ittakes long to impregnate the reinforcing fibers with the resincomposition. When the component (a) comprises plural epoxy resins, theviscosity of the mixture is used.

[0038] Examples of component (a) are aromatic glycidyl ether obtainablefrom phenol having plural hydroxyl groups, aliphatic glycidyl etherobtainable from alcohol having plural hydroxyl groups, glycidyl amineobtainable from amine, glycidyl ester obtainable from carboxylic acidhaving plural carboxyl groups, polyepoxide obtainable by oxidizingcompounds having plural double bonds in the molecule, and the like.

[0039] Examples of aromatic glycidyl ether are diglycidyl etherobtainable from bisphenol, such that, diglycidyl ether of bisphenol A,diglycidyl ether of bisphenol F, diglycidyl ether of bisphenol AD,diglycidyl ether of bisphenol S, and diglycidyl ether of tetrabromobisphenol A, and the like; polyglycidyl ether of novolac obtainable fromphenol, alkyl phenol, halogenated phenol, and the like; diglycidyl etherof resorcinol, diglycidyl ether of hydroquinone, diglycidyl ether of4,4′-dihydroxy-3,3′,5,5′-tetramethylbiphenyl, diglycidyl ether of1,6-dihydroxynaphthalene, diglycidyl ether of9,9′-bis(4-hydroxyphenyl)fluorene, triglycidyl ether oftris(p-hydroxyphenyl)methane, tetraglycidyl ether oftetrakis(p-hydroxyphenyl)ethane, diglycidyl ether having oxazolidonebackbone obtainable by reacting diglycidyl ether of bisphenol A withdi-functional isocyanate, and the like.

[0040] Examples of aliphatic glycidyl ether are diglycidyl ether ofethylene glycol, diglycidyl ether of propylene glycol, diglycidyl etherof 1,4-butanediol, diglycidyl ether of 1,6-hexanediol, diglycidyl etherof neopentyl glycol, diglycidyl ether of cyclohexane dimethanol,diglycidyl ether of glycerin, triglycidyl ether of glycerin, diglycidylether of trimethylolethane, triglycidyl ether of trimethylolethane,diglycidyl ether of trimethylolpropane, triglycidyl ether oftrimethylolpropane, tetraglycidyl ether of pentaerythritol, diglycidylether of dodecahydro bisphenol A, diglycidyl ether of dodecahydrobisphenol F, and the like.

[0041] Examples of glycidyl amine are diglycidylaniline,tetraglycidyldiaminodiphenylmethane,N,N,N′,N′-tetraglycidyl-m-xylylenediamine, and 1,3-bis(diglycidylaminomethyl)cyclohexane; triglycidyl-m-aminophenol andtriglycidyl-p-aminophenol having both structures of glycidyl ether andglycidyl amine, and the like.

[0042] Examples of glycidyl ester are diglycidyl ester of phthalic acid,diglycidyl ester of terephthalic acid, diglycidyl ester ofhexahydrophthalic acid, diglycidyl ester of dimer acid, and the like.

[0043] In addition to the above, triglycidylisocyanurate may be used andepoxy resins having an epoxycyclohexane ring and epoxylated soybean oil,which are obtainable by oxidizing a compound having plural double bondsin the molecule, and the like, may also be used.

[0044] Among them, diglycidyl ether of bisphenol A, diglycidyl ether ofbisphenol F, and diglycidyl ether of bisphenol AD are preferably usedbecause the viscosity of the resin composition thereof, heat resistance,and mechanical properties such as elastic modulus of resulting curedresin products are good.

[0045] Component (b) of the present invention is an anionicpolymerization initiator used as a curing agent of epoxy resins. Ananionic polymerization initiator is defined herein as a compound capableof initiating anionic polymerization of the epoxy resin.

[0046] The amount of the component (b) is preferably 0.1 to 10 parts byweight, more preferably 0.1 to 5 parts by weight based on 100 parts byweight of the component (a). If the amount is greater than these ranges,the excess component (b) functions as a plasticizer so that the heatresistance and the mechanical properties such as elastic modulus of theresulting cured resin product tend to be poor.

[0047] Examples of the component (b) are hydroxides, such as sodiumhydroxide, potassium hydroxide, and quaternary ammonium hydroxide;alkoxides, such as sodium alkoxide; iodides, such as sodium iodide,potassium iodide, quaternary ammonium iodide; tertiary amine, and thelike.

[0048] Among them, tertiary amine is preferably used as component (c)because of its high ability as an anionic polymerization initiator.

[0049] Examples of the tertiary amine are triethylamine,dimethylbenzylamine, 2,4,6-tris(dimethylaminomethyl)phenol,1,5-diazabicyclo[4.3.0]nona-5-en, 1,8-[5.4.0]undeca-7-en, pyridine,4-dimethylaminopyridine, 3-dimethylaminopropylamine,3-diethylaminopropylamine, 3-dibutylaminopropylamine,2-diethylaminoethylamine, 1-diethylamino-4-aminopentane,N-(3-aminopropyl)-N-methylpropanediamine, 1-(2-aminoetheyl)piperazine,1,4-bis(2-aminoethyl)piperazine, 3-(3-dimethylaminopropyl)propylamine,1,4-bis(3-aminopropyl)piperazine, 4-(2-aminoethyl)morpholine,4-(3-aminopropryl)morpholine, imidazole derivatives, and the like.

[0050] Among them, an imidazole derivative is preferably used ascomponent (c) because it has high ability as an anionic polymerizationinitiator, and it can cure the epoxy resin composition in a short time.

[0051] Examples of imidazole derivative are imidazole,2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole,2-heptadecylimidazole, 2-phenylimidazole, 1,2-dimethylimidazole,2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole,1-benzyl-2-phenylimidazole, 1-benzyl-2-methylimidazole,1-cyanoethyl-2-methylimidazole, 1-aminoethyl-2-methylimidazole, and thelike.

[0052] Among them, imidazoles represented by the following formula I arepreferably used as component (c) because they have extremely highability as an anionic polymerization initiator and they can cure theepoxy resin composition in a short time.

[0053] wherein, R¹ represents a member selected from the groupconsisting of hydrogen atom, a methyl group, an ethyl group, a benzylgroup, or a cyanoethyl group; R², R³, and R⁴ each represent any memberselected from the group consisting of a hydrogen atom, a methyl groupand an ethyl group.

[0054] The component (c) of the present invention is a proton donor. Aproton donor is defined herein as a compound having active hydrogenwhich can be donated as a proton to basic compounds.

[0055] Also, said active hydrogen of the present invention is definedherein as hydrogen that can be donated to basic compounds as a proton.

[0056] The proton donor functions as a chain transfer agent if theresulting anionic species after a proton donation have moderatenucleophilicity. If suitable chain transfer reaction occurs at thebeginning of a polymerization, it inhibits the epoxy resin from becominga too high molecular weight polymer or inhibits gelation which preventsincrease of viscosity. As a result, it is possible to secure longinjection time. In addition, the presence of a proton donor enhancesanionic polymerization. By using these two advantageous properties, itis possible to design a thermosetting resin composition that preventsincrease of viscosity at the beginning of a reaction and acceleratescompletion of a curing reaction.

[0057] Based on the above, preferred examples for component (c) areproton donors selected from the group consisting of an alcohol, aphenol, a mercaptan, a carboxylic acid and a 1,3-dicarbonyl compound.The component (c) may be a compound that belongs to multiple categoriesof these exemplary compounds, such as a compound having an alcoholichydroxyl group and a phenolic hydroxyl group.

[0058] The component of (a) may include compounds that have a hydroxylgroup in the molecule, in such a case, they are not included in thecomponent of (c).

[0059] The amount of the component (c) is 1 to 30 parts by weight andpreferably 1 to 20 parts by weight based on 100 parts by weight of thecomponent (a). If the amount is less than these ranges, it may bedifficult to decrease curing time while preventing increase ofviscosity. If the amount is greater than these ranges, heat resistanceand mechanical properties such as elastic modulus tend to be poor.

[0060] The component (c) is introduced to the crosslinking structure byreacting with the epoxy resins, and influences heat resistance andmechanical properties of the cured resin product. Thus, it is preferablethat the component (c) is a compound having two or more active hydrogenin one molecule. When compounds having one active hydrogen in onemolecule are used, crosslinking density of the resulting cured resinproduct tends to be lowered so that heat resistance and mechanicalproperties such as elastic modulus, may be poor.

[0061] The compounds that have an aromatic ring, cycloalkane ring or acycloalkene ring are preferably used as component (c) because the heatresistance and mechanical properties of the resulting cured resinproducts such elastic modulus, are good.

[0062] An alcohol is preferably used as the component (c) because theresulting anion species after a proton donation has the most preferablenucleophilicity.

[0063] An alcohol having a boiling point at atmospheric pressure of morethan 100° C., preferably more than 140° C., and further preferably morethan 180° C. at atmospheric pressure, is preferable. If the boilingpoint is low, voids may occur in the fiber-reinforced compositematerials due to evaporation of the component (c) during injection orcuring. When two or more components (c) are used, all such componentsshould satisfy the above conditions.

[0064] An alcohol of which the hydroxyl equivalent weight is more than100 g/mol, preferably more than 120 g/mol, and further preferably 140g/mol, is preferable. If the equivalent weight is less than theseranges, the polarity of the alcohol tends to be too high. Thus, itscompatibility with epoxy resins tends to be insufficient, and difficultyin handling may occur. When two or more alcohols are used, a harmonicaverage of hydroxyl equivalent weights that is weighted by weightfractions of the alcohols, is used as the hydroxyl equivalent weight ofthe mixture.

[0065] Examples of preferred alcohols are: 1,2-ethanediol (Bp=197,He=31), 1,2-propanediol (Bp=187, He=38), 1,3-propanediol (Bp=215,He=38), 1,3-butanediol (Bp=208, He=45), 1,4-butanediol (Bp=228, He=45),1,5-pentanediol (Bp=239, He=52), 1,1-dimethyl-1,3-propanediol (Bp=203,He=52), 2,2-dimethyl-1,3-propanediol (Bp=211, He=52),2-methyl-2,4-pentanediol (Bp=198, He=59), 1,4-cyclohexanediol (Bp=150[2.66 kPa], He=58), 1,4-cyclohexanedimethanol (Bp=162 [1.33 kPa]),diethyleneglycol (Bp=244, He=53), triethyleneglycol (Bp=287, He=75),dodecahydro bisphenol A (Bp: no data, He=120), ethylene oxide adduct ofbisphenol A represented by the following formula II (Bp: no data,He=158), propylene oxide adduct of bisphenol A represented by thefollowing formula IV (Bp: no data, He=172), ethylene oxide adduct ofdodecahydro bisphenol A represented by the following formula IV (Bp: nodata, He=164), propylene oxide adduct of dodecahydro bisphenol Arepresented by the following formula V (Bp: no data, He=178), glycerin(Bp=290, He=31), trimethylolethane (Bp=165 to 171 [0.864 kPa], He=40),trimethylolpropane (Bp=292, He=45), and the like, wherein, Bp meansboiling point (° C.), and He means hydroxyl equivalent (g/mol). Examplesof alcohols that comprise four hydroxyl groups in one molecule arepentaerythritol (Bp: no data, He=34), and the like.

[0066] Examples of phenols having one active hydrogen in one moleculeare phenol, cresol, ethylphenol, n-propylphenol, isopropylphenol,n-butylphenol, sec-butylphenol, tert-butylphenol, cyclohexylphenol,dimethylphenol, methyl-tert-butylphenol, di-tert-butylphenol,chlorophenol, bromophenol, nitrophenol, methoxyphenol, methylsalicylate, and the like. Examples of phenols having two active hydrogenin one molecule are hydroquinone, resorcinol, catechol,methylhydroquinone, tert-butylhydroquinone, benzylhydroquinone,phenylhydroquinone, dimethylhydroquinone, methyl-tert-butylhydroquinone,di-tert-butylhydroquinone, trimethylhydroquinone, methoxyhydroquinone,methylresorcinol, tert-butylresorcinol, benzylresorcinol,phenylresorcinol, dimethylresorcinol, methyl-tert-butylresorcinol,di-tert-butylresorcinol, trimethylresorcinol, methoxyresorcinol,methylcatechol, tert-butylcatechol, benzylcatechol, phenylcatechol,dimethylcatechol, methyl-tert-butylcatechol, di-tert-butylcatechol,trimethylcatechol, methoxycatechol, biphenols such as biphenol,4,4′-dihydroxy-3,3′,5,5′-tetramethylbiphenyl,4,4′-dihydroxy-3,3′,5,5′-tetra-tert-butylbiphenyl, and the like,bisphenols such as bisphenol A, 4,4′-dihydroxy-3,3′,5,5′-tetramethylbisphenol A, 4,4′-dihydroxy-3,3′,5,5′-tetra-tert-butyl bisphenol A,bisphenol F, 4,4′-dihydroxy-3,3′,5,5′-tetramethyl bisphenol F,4,4′-dihydroxy-3,3′,5,5′-tetra-tert-butyl bisphenol F, bisphenol AD,4,4′-dihydroxy-3,3′,5,5′-tetramethyl bisphenol AD,4,4′-dihydroxy-3,3′,5,5′-tetra-tert-butyl bisphenol AD, and compoundsrepresented by the following formulas VI to XII, terpenephenol,compounds represented by the following formulas XII to XIV, and thelike. Examples of phenols having three active hydrogen in one moleculeare trihydroxybenzene, tris(p-hydroxyphenyl)methane, and the like.Examples of phenols having four active hydrogen in one molecule aretetrakis(p-hydroxyphenyl)ethane, and the like. In addition to the above,other examples may include novolac of phenols such as phenol,alkylphenol, and halogenated phenol.

[0067] Examples of mercaptans having one active hydrogen in one moleculeare methanethiol, ethanethiol, 1-propanethiol, 2-propanethiol,1-butanethiol, 2-methyl-1-propanethiol, 2-butanethiol,2-methyl-2-propanethiol, 1-pentanethiol, 1-hexanethiol, 1-heptanethiol,1-octanethiol, cyclopentanethiol, cyclohexanethiol, benzylmercaptan,benzenethiol, toluenethiol, chlorobenzenethiol, bromobenzenethiol,nitrobenzenethiol, methoxybenzenethiol, and the like. Examples ofmercaptans having two active hydrogen in one molecule are1,2-ethanedithiol, 1,3-propanedithiol, 1,4-butanedithiol,1,5-pentanedithiol, 2,2′-oxydiethanethiol, 1,6-hexanedithiol,1,2-cyclohexanedithiol, 1,3-cyclohexanedithiol, 1,4-cyclohexanedithiol,1,2-benzenedithiol, 1,3-benzenedithiol, 1,4-benzenedithiol, and thelike.

[0068] Examples of carboxylic acids having one active hydrogen in onemolecule are formic acid, acetic acid, propionic acid, butyric acid,valeric acid, caproic acid, caprylic acid, lauric acid, myristic acid,palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid,cyclohexanecarboxylic acid, phenylacetic acid, phenoxyacetic acid,benzoic acid, toluic acid, chlorobenzoic acid, bromobenzoic acid,nitrobenzoic acid, methoxybenzoic acid, and the like. Examples ofcarboxylic acids having two active hydrogen in one molecule are malonicacid, methylmalonic acid, phenylmalonic acid, succinic acid, fumaricacid, maleic acid, glutaric acid, diglycolic acid, thioglycolic acid,adipic acid, pimelic acid, cyclohexane-1,2-dicarboxylic acid,cyclohexane-1,3-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid,phthalic acid, isophthalic acid, terephthalic acid, and the like.

[0069] Examples of 1,3-dicarbonyl compounds are 2,4-pentanedione,3-methyl-2,4-pentanedione, 3-ethyl-2,4-pentanedione, 3,5-heptanedione,4,6-nonanedione, 2,6-dimethyl-3,5-heptanedione,2,2,6,6-tetramethyl-3,5-heptanedione, 1-phenyl-1,3-butanedione,1,3-diphenyl-1,3-propanedione, 1,3-cyclopentanedione,2-methyl-1,3-cyclopentanedione, 2-ethyl-1,3-cyclopentanedione,1,3-cyclohexanedione, 2-methyl-1,3-cyclohexanedione,2-ethyl-cyclohexanedione, 1,3-indandione, ethyl acetoacetate, diethylmalonate, and the like.

[0070] In the epoxy resin compositions of the present invention, thecomponent (a) should be liquid at least at the injection temperature,and the components (b) and (c) should be uniformly dissolved incomponent (a). It is not preferable that some part of these componentsis solid, or makes separated phase even if all of these are liquid,because partial heterogeneity of compositions may occur duringimpregnation. However, even if it is impossible for these components tomake homogeneous solution at room temperature, they can be used if theycan satisfy the above conditions through heating.

[0071] In addition to the above components, the epoxy resin compositionsof the present invention may comprise a surfactant, an internal releaseagent, a pigment, a flame retardant, antioxidant, UV absorbent, and thelike.

[0072] It is most preferable that these additives are homogeneouslydissolved in the epoxy resin composition. Although these additives arenot homogeneously dissolved in the epoxy resin composition, there are noproblems if they maintain a stable colloid in the form of a droplet or aparticle. In this case, the diameter of the droplet or the particle ispreferably less than 1 μm and more preferably less than 0.3 μm. Ifdiameter of the droplet or the particle is larger than these ranges, itmay be difficult for the droplet or particle to pass gaps in thereinforcing fibers, so that heterogeneity of compositions may occur.

[0073] The initial viscosity of the epoxy resin compositions of thepresent invention at 25° C. is preferably 1 to 30,000 mPa s, morepreferably 1 to 20,000 mPa s and further preferably 1 to 10,000 mPa s.If the viscosity is higher than these ranges, the initial viscosity ofthe epoxy resin compositions at the injection temperature of 60 to 180°C. may become high, so that it takes long time to impregnate thereinforcing fibers with the resin composition.

[0074] The epoxy resin composition of which initial increase of theviscosity is low, and which have lengthened injection time and shortenedcuring time are preferable for the present invention.

[0075] When curing reaction is fast, it is difficult to monitor thechange of the viscosity by conventional methods. Monitoring the changeof ionic viscosity by means of dielectric measurement is, however,possible even though the curing reaction is fast. The ionic viscositymay be used for monitoring a progress of curing reaction as well asinitial viscosity change because it can be measured after gelation,increases along with a progress of curing and is saturated along withcompletion of curing. A normalized logarithmic value of which theminimum has been set to 0% and maximum (saturation) has been set for100% is called the cure index. This index is used to describe a curingprofile of a thermosetting resin. By using the time required for thecure index to reach 10% as a standard for initial increase of viscosity,and time required for the cure index to reach 90% as a standard forcuring time, suitable conditions wherein initial increase of viscosityis low and curing time is short, may be conveniently described. It ispreferable that the epoxy resin composition of the present inventionsatisfies the following conditions (1) to (3) at a specific temperatureT between 60 to 180° C. It is more preferable that the epoxy resincomposition of the present invention satisfies the following conditions(1) to (3′) at a specific temperature between 60 to 180° C.

1≦t₁₀≦10  (1)

3≦t₉₀≦30  (2)

1<t ₉₀ /t ₁₀≦3  (3)

1<t ₉₀ /t ₁₀≦2.5  (3′)

[0076] wherein,

[0077] t₁₀: time required for the cure index to reach 10% from thebeginning of the measurement, which is measured by dielectricmeasurement at the temperature T (min.)

[0078] t₉₀: time required for the cure index to reach 90% from thebeginning of the measurement at the temperature T, which is measured bydielectric measurement (min.)

[0079] As curing proceeds, the glass transition temperature of the resincomposition rises. In general, demolding is carried out after the glasstransition temperature of the resin composition exceeds the curingtemperature. Thus, the time required for the glass transitiontemperature of the cured resin product to reach curing temperature maybe used as a standard for curing time. It is preferable that the epoxyresin composition of the present invention satisfies the followingconditions (4) to (6). It is more preferable that the epoxy resincomposition of the present invention satisfies the following conditions(4) to (6′).

1≦t₁₀≦10  (4)

3≦t_(v)≦30  (5)

1<t _(v) /t ₁₀≦3.0  (6)

1<t _(v) /t ₁₀≦2.5  (6′)

[0080] wherein,

[0081] t₁₀: time required for the curing index to reach 10% from thebeginning of the measurement, which is measured by dielectricmeasurement at the temperature T(min.)

[0082] t_(v): time required for the glass transition temperature of thecured resin product to reach the temperature T from the beginning of themeasurement, that is vitrification time, which is measured at thetemperature T (min.)

[0083] The epoxy resin composition of the present invention have thecharacteristic of which the initial increase of viscosity is low, thatis, injectable time is long, and curing time is short. Therefore, it issuitable for the RTM method where the mold temperature is maintainedconstant from injection to demolding.

[0084] The epoxy resin composition of the present invention is alsosuitable for the RTM method where the mold temperature is raised aftertermination of the injection to cure the resin composition. And theepoxy resin composition of the present invention has the advantage ofshorten the molding time, too.

[0085] The epoxy resin composition of the present invention isapplicable to all methods where a liquid thermosetting resins is used,such as hand lay-up method, pultrusion method, filament winding method,and the like, as well as RTM method. And the epoxy resin composition ofthe present invention has the advantage to shorten the molding time inall these methods.

[0086] A process for producing fiber-reinforced composite materials isdescribed below.

[0087] In accordance with the present invention, it is possible toproduce fiber-reinforced composite materials with high Vf with goodproductivity.

[0088] In the RTM method of the present invention, it is necessary thatthe mold temperature be maintained at the specific temperature T_(m)that is between 60 to 180° C., and the following conditions (7) to (9)and preferably (7) to (9′) be satisfied.

ti≦10  (7)

t_(m)≦60  (8)

1<t _(m) /t _(i)≦6.0  (9)

1<t _(m) /t _(i)≦5.0  (9′)

[0089] wherein,

[0090] t_(i): time from the beginning of injection to the termination ofinjection (min.)

[0091] t_(m): time from the beginning of injection to the beginning ofdemolding (min.)

[0092] In the RTM method of the present invention, the mold temperatureis maintained at the specific temperature T_(m) between 60 to 180° C. toomit raising and lowering of the mold temperature and, as a result, toshorten molding time. However, some variation of the mold temperaturedepending on time and place is somewhat allowed. Specifically,difference ΔT between T_(m) and the temperature measured at any point ofa surface of a cavity during a period from the beginning of injection tothe beginning of demolding should be −20 to 20° C., preferably −10 to10° C., and more preferably −5 to 5° C. If there are any portion whereΔT is too large, viscosity of the resin composition increases to giverise to gelation and to prevent impregnation. If there are any portionwhere ΔT is too small, partial failure of curing occurs, which is notpreferable.

[0093] Time t_(i) used herein means time from the beginning of injectionto the termination of injection. Here, the beginning of injection meansa point when the resin composition starts to pour into the mold, and thetermination of injection means a point when the resin composition isstopped to supply into the mold. When the mold has plural inlets ofwhich time of injection at each inlets are different from one another,or termination time of injection at each inlets are different from oneanother, t_(i) is set for time from the last beginning of injection tothe last termination of injection.

[0094] Time t_(m) used herein means time from the beginning of injectionto the beginning of demolding. When the mold has plural inlets of whichbeginning time of injection at each inlets are different from oneanother, t_(m) is set for time from the last beginning of injection tothe beginning of the demolding.

[0095] Epoxy resin compositions, unsaturated polyester resincompositions, vinyl ester resin compositions, phenolic resincompositions, maleimide resin compositions, and cyanate ester resincompositions are preferably used in the RIM method of the presentinvention.

[0096] In the RTM method of the present invention, it is difficult tomeasure the viscosity at the temperature T_(m) directly because theviscosity of the resin composition varies rapidly. However, it ispossible to estimate the initial viscosity at the temperature T_(m) bymeasuring the viscosity at low temperature, which is easy to measure,and calculating by the formula WLF represented as formula A.

In(η/η₀)=−[A(T−T ₀)]/[B+(T−T ₀)]  [Formula A]

[0097] wherein, In represents natural logarithm, T represents absolutetemperature (K), T₀ represents reference temperature (K), η representsviscosity of a resin composition at T (mPa s), η₀ represents viscosityof a resin composition at T₀ (mPa s), and A and B represent constantsthat are inherent to a liquid.

[0098] Specifically, four to six temperatures at which viscosity is easyto measure are selected, and one of them is set for T₀. Then, viscosityat each temperature is measured. Constants A and B are calculated bylinear regression analysis using formula B. Finally, initial viscosityat T_(m) is determined by using these parameters.

[0099] In the RTM method of the present invention, if initial viscosityof the resin composition at T_(m) is low, impregnation of reinforcingfibers with the resin compositions is good. Therefore, initial viscosityat T_(m) measured by the WLF formula is preferably 0.1 to 300 mPa s,more preferably 0.1 to 200 mPa s, and further preferably 0.1 to 100 mPas.

[0100] In the RTM method of the present invention, glass transitiontemperature of fiber-reinforced composite materials after t_(m) from thebeginning of injection is preferably greater than T_(m)−15° C. and morepreferably greater than T_(m). If the glass transition temperature isless than these ranges, matrix resin is likely to flow or creep atT_(m), and fiber-reinforced composite materials may be deformed by forceexerted when demolding is carried out.

[0101] In the RTM method of the present invention, Vf offiber-reinforced composite materials is preferably 40 to 85% and morepreferably 45 to 85% to obtain fiber-reinforced composite materials thatare light-weight and excellent in their mechanical properties, such asstrength and elastic modulus. If Vf is less than these ranges,mechanical properties of the fiber-reinforced composite materials, suchas strength and elastic modulus, may be insufficient. If Vf is greaterthan these ranges, it may be necessary to inject the resin compositionsinto a mold in which reinforcing fibers are placed in a very highdensity. Thus, it may be difficult to inject the resin composition intothe mold.

[0102] In the RTM method of the present invention, a plastic film, ametal or plastic plate, connection parts such as a bolt, a nut, a Ulink, a hinge and the like, and core materials such as a foam core, ahoneycomb-core, and the like, in addition to the reinforcing fibers, maybe placed in the mold.

[0103] In the RTM method of the present invention, reinforcing fibersubstrates such as strands, fabrics, mats, knits, and braids are placedin the mold prior to injection of the resin compositions. Reinforcingfiber substrates may be cut and laminated to the desired shape andplaced in the mold with other materials such as core materials, ifnecessary. Also, preforms of the reinforcing fiber substrates formed tothe desired shape by methods, such as stitching or press with heat afterapplying a small amount of tackifier may be placed in the mold. Acombination of reinforcing fiber substrates and other materials such ascore materials may be used for the preforms.

[0104] In the RTM method of the present invention, a closed mold havinga cavity enclosed by only stiff materials or an open mold having acavity enclosed by stiff materials and bagging film may be used.

[0105] In the RTM method of the present invention, metals, such ascarbon steel, steel alloy, cast iron, aluminum, aluminum alloy, nickelalloy, FRP (Fiber Reinforced Plastic) or wood may be used for thematerials of the mold. Among them, metals are preferable because theirthermal conductivity is good.

[0106] Examples of bagging film to be used for the open mold arepolyamide, polyimide, polyester, silicone, and the like.

[0107] In the RTM method of the present invention, the closed mold ispreferably used because the closed mold makes it possible to inject aresin composition by pressing and facilitates removal of heat producedby curing of the resin compositions.

[0108] The mold may be provided with the function to heat by circulationof a heat medium or a conventional heater.

[0109] In the RTM method of the present invention, the mold has inletsto inject a resin composition and outlets to flow out a resincomposition. There are no limitation to the number or places of theinlets and outlets.

[0110] It is preferable to introduce a resin composition into a cavitythrough a fan gate or a film gate, specially when planarfiber-reinforced composite materials are molded.

[0111] In the RTM method of the present invention, it is preferable toapply release agents to the surface of the mold to demold the resultingfiber-reinforced composite materials easily. Examples of release agentsinclude the silicone type, fluorine type, plant oil type, wax type, PVAtype, and the like.

[0112] In the RTM method of the present invention, a gel coat or a gelcoat sheet such as disclosed in Japanese patent laid-open publicationNo. 1993-318468 and Japanese patent laid-open publication No.2001-288230 may be used to provide the properties to surface such ascolor, gloss, hardness, water resistance, weatherability, and the like.

[0113] In the RTM method of the present invention, the shorter is theinjection time, the shorter is the molding time. In cases when planarfiber-reinforced composite materials are molded, it is preferable torapidly distribute the resin composition in a planar form in the mold,and then, impregnate it mainly in the direction of thickness of thereinforcing fiber substrates to decrease the injection time. For this, aresin distribution medium, a mold having a resin distribution grooves atthe surface of a cavity, and a core having a resin distribution groovesare preferably used.

[0114] As disclosed in U.S. Pat. No. 4,902,215, a resin distributionmedium means a planar structure through which resin compositions areeasily flowed. Metallic nets are preferably used because their heatresistance is high, and they do not dissolve in matrix resins. Plasticnets which hardly dissolve or swell even if they contact with matrixresins, such as polyethylene, polypropylene, nylon, polyester, and thelike are also preferably used.

[0115] When a mold has a resin distribution grooves at the surface of acavity, it is preferable that the cross section of the grooves is in ashape that does not inhibit demolding such as a rectangle, trapezoid,triangle or semicircle. Arrangement of the grooves depends on the shapeof the cavity. In general, although there are no limitations to thearrangement of the grooves, parallel lines or a lattice is preferablyused. For a mold having a planar cavity, the grooves must be placed atleast at one surface of the cavity to introduce a resin composition froman inlet to the grooves. Opposing surface may or may not have grooves.

[0116] When a foam core or balsa core is used, the resin distributiongrooves may be placed at the core. It is preferable that the grooves areplaced on the entire surface where the core contacts with thereinforcing fiber substrates. Arrangement of the grooves depends on theshape of the cavity and the core. Although there are no limitations tothe arrangement of the grooves, parallel lines or a lattice ispreferably used. When a core having the grooves is used, it is necessaryto design a mold in which an injected resin composition is introduced togrooves at the beginning. As disclosed in U.S. Pat. No. 5,958,325, acore having resin main feeder grooves and microgrooves may be used.

[0117] In the RTM method of the present invention, a pre-mixed singleresin composition in a single tank may be transferred and injected intoa mold. Alternatively, a plurality of liquids in separate tanks may betransferred to a mixer where the transferred liquids are mixed togetherto form resin composition, which is then injected into a mold.

[0118] In the RTM method of the present invention, the injectionpressure (pressure when resin compositions are injected into a mold) ispreferably 0.1 to 1.0 MPa and more preferably 0.1 to 0.6 MPa. Ifinjection pressure is too low, injection time may become too long. Ifinjection pressure is too high, it may not be economical becauseexpensive plumbing, molds, and presses are required. Various pumps orpressing of a tank is used to transfer liquids.

[0119] In the RTM method of the present invention, it is preferable touse suction from outlets by a vacuum pump and the like when the resincomposition is injected into a mold. Suction is effective to shorten theinjection time and to prevent occurrence of dry areas or voids in thefiber-reinforced composite materials.

[0120] In the RTM method of the present invention, post-cure may beperformed in a heater such as an oven after demolding to increase heatresistance of the fiber-reinforced composite materials. It is preferablethat the post-cure is performed at 100 to 200° C. for 10 to 480 minutes.

[0121] The fiber-reinforced composite materials of the present inventionare described below.

[0122] For the fiber-reinforced composite materials of the presentinvention, glass fibers, aramid fibers, carbon fibers and boron fibersare preferably used as reinforcing fibers. Among them, carbon fibers arepreferably used because fiber-reinforced composite materials oflightweight and good mechanical properties, such as strength and elasticmodulus, can be obtained.

[0123] The reinforcing fibers may be one of chopped fibers, continuousfibers or a combination thereof. Continuous fibers are preferablebecause their handling is easy and it is possible to obtain high Vffiber-reinforced composite materials by using them.

[0124] In the fiber-reinforced composite materials of the presentinvention, the reinforcing fibers may be used in the form of strands.However, reinforcing fiber substrates that are processed intoreinforcing fibers in the form of mats, woven fabrics, knits, braids orunidirectional sheet are preferably used.

[0125] Among them, woven fabrics are preferably used because theirhandling is easy, and fiber-reinforced composite materials having highVf can be easily obtained.

[0126] A ratio of real volume of the reinforcing fibers to apparentvolume of the fabrics is set for packing fraction of the fabrics. Thepacking fraction is determined by the formula W/(1000 t ρ_(f)), whereinW represents areal weight (g/m²), t represents thickness (mm), and ρ_(f)represents density of the reinforcing fibers (g/cm³). The areal weightand thickness of the fabrics can be determined according to JIS R 7602.It is easy to produce fiber-reinforced composite materials with high Vffrom fabrics with high packing fraction. Thus, the packing fraction ofthe fabrics is preferable 0.10 to 0.85, more preferably 0.40 to 0.85,and further preferably 0.50 to 0.85.

[0127] Vf of the fiber-reinforced composite materials is preferably 40to 85%, and more preferably 45 to 85% to obtain fiber-reinforcedcomposite materials which have high specific strength and specificelastic modulus.

[0128] The specific strength of the fiber-reinforced composite materialsof the present invention is preferably greater than 250 MPa cm³/g, morepreferably greater than 300 MPa cm³/g, and further preferably greaterthan 350 MPa cm³/g if lightweight and high strength fiber-reinforcedcomposite materials are required. The specific strength (MPa cm³/g) canbe calculated from the following formula B using tensile strength σ(MPa) determined according to ASTM D 3039 and density of thefiber-reinforced composite materials ρ_(c) (g/cm³) determined accordingto ASTM D 792.

specific strength=σ/ρ_(c)  [Formula B]

[0129] In general, fiber-reinforced composite materials are anisotropic.Therefore, tests are made in a direction where maximum strength isobtained.

[0130] The specific elastic modulus of the fiber-reinforced compositematerials of the present invention is preferably greater than 28 GPacm³/g. more preferably greater than 32 GPa cm³/g, and further preferablygreater than 34 GPa cm³/g if lightweight and high elastic modulusfiber-reinforced composite materials are required. The specific elasticmodulus (GPa cm³/g) can be calculated from the following formula C usingtensile modulus E (GPa) determined according to ASTM D 3039 and densityof the fiber-reinforced composite materials ρ_(c) (g/cm³) determinedaccording to ASTM D 792.

specific elastic modulus=E/ρ _(c)  [Formula C]

[0131] In general, fiber-reinforced composite materials are anisotropic.Therefore, tests are made in a direction where maximum elastic modulusis obtained.

[0132] The preferred form of the fiber-reinforced composite materials isa monolithic plate. Another preferred form of the fiber-reinforcedcomposite materials is a sandwich structure in which thefiber-reinforced composite materials are positioned on both surfaces ofthe core.

[0133] Still another preferred form of the fiber-reinforced compositematerials is a canape structure in which single planar fiber-reinforcedcomposite materials are positioned on one surface of the core.

[0134] Examples of a core of sandwich structure and canape structure area honeycomb-core made of aluminum or aramid, a foam core made ofpolyurethane, polystyrene, polyamide, polyimide, polyvinyl chloride,phenolic resin, acrylic resin, epoxy resin, and the like, wood includingbalsa, and the like. Among these, the foam core is preferably usedbecause it can produce lightweight fiber-reinforced composite materials.

[0135] The density of the core is preferably 0.02 to 0.10 g/cm³ and morepreferably 0.02 to 0.08 g/cm³ to obtain lightweight fiber-reinforcedcomposite materials. The density of the core can be determined accordingto ISO 845.

[0136] If the glass transition temperature of the core is low, it islikely that the core deforms during molding. Therefore, the glasstransition temperature of the core is preferably more than 80° C., morepreferably more than 100° C. and further preferably more than 120° C.

[0137] In the sandwich structure fiber-reinforced composite materials,the higher is the shear modulus of elasticity of the core, the higher isthe flexural stiffness. Therefore, the shear modulus of elasticity ispreferably more than 2.0 MPa, more preferably more than 4.0 MPa, andfurther preferably more than 6.0 Mpa. The shear modulus of elasticity ofthe core is determined according to ASTM C 273.

[0138] If the independent bubble content of the core is great, it isdifficult for the resin composition to penetrate into the core.Therefore, the independent bubble content of the core is preferably morethan 0.70, more preferably more than 0.80, and further preferably morethan 0.90. The independent bubble content of the core is determinedaccording to ASTM D 1940.

[0139] When the fiber-reinforced composite materials of the presentinvention are used for the stylish surface such as the outer skin ofautomobiles, the surface roughness R_(a) of at least one side of thefiber-reinforced composite materials is preferably less than 1.0 μm,more preferably less than 0.6 μm, and further preferably less than 0.4μm. The surface roughness R_(a) is determined according to ISO 468.

[0140] The fiber-reinforced composite materials of the present inventionare particularly suitable for structural parts, outer skins andaerodynamic parts of transports such as spacecrafts including rockets,artificial satellites, and the like, aircrafts, trains, marines,automobiles, motorcycles, bicycles, and the like, because they arelightweight and have good mechanical properties such as strength andelastic modulus.

[0141] Because the productivity of the fiber-reinforced compositematerials of the present invention is high, they are preferably used forstructural parts, outer skins and aerodynamic parts of motorcycles andautomobiles of mass production. Specific examples are structural partssuch as platforms, outer skins of automobiles such as front apron, hood,roof, hard top (a removable roof of a convertible car), a piller, trunklid, door, fender and side mirror cover, and the like, and aerodynamicparts such as front air dam, rear spoiler, side air dam, engine undercover, and the like.

[0142] The fiber-reinforced composite materials of the present inventioncan be used for other applications besides the above applications.Specific examples are interior trim materials of automobiles such as aninstrument panel.

EXAMPLES

[0143] The following examples will explain the present invention morespecifically. Each property was determined by the following methods.Also, the following resin components were used in the examples.

[0144] Component a

[0145] “Epo Tohto” YD128: registered trademark, produced by Tohto KaseiCo., Ltd., epoxy resin (diglycidylether of bisphenol A)

[0146] Component b

[0147] 2-methylimidazole: produced by Shikoku Kasei Kogyo Co., Ltd.,imidazole derivative

[0148] Component c

[0149] glycerin: produced by Tokyo Kasei Kogyo Co., Ltd., alcohol

[0150] 1,2-ethanediol: produced by Tokyo Kasei Kogyo Co., Ltd., alcohol

[0151] benzyl alcohol: produced by Wako Junyaku Kogyo, Ltd., alcohol

[0152] isopropyl alcohol: produced by Tokyo Kasei Kogyo Co., Ltd.,alcohol

[0153] propylene glycol: produced by Wako Junyaku Kogyo, Ltd., alcohol

[0154] “Rikaresin” PO-20: registered trademark, produced by Shin NipponRika Co., Ltd., alcohol (propylene oxide adduct of bisphenol A)

[0155] 2,4-dimethylphenol: produced by Tokyo Kasei Kogyo Co., Ltd.,phenol propionic acid: produced by Tokyo Kasei Kogyo Co., Ltd.,carboxylic acid

[0156] Measurement of Viscosity of a Resin Composition

[0157] Viscosity of the component (a) and that of the resin compositionjust after the composition was prepared, were measured according to ISO2884-1 by using the cone-and-plate rotary viscometer. The viscometer wasTVE-30H manufactured by Toki Sangyo Co., Ltd. The rotor used was 1°34′×R24. An amount of each sample was 1 cm³.

[0158] Method for Estimating Viscosity at the Temperature T_(m) by Usingthe Formula WLF

[0159] Viscosity of the resin composition was measured at 10, 30, 50 and70° C. according to the above method. The reference temperature T₀ wasset for 10° C. The constants A and B were calculated by linearregression analysis by using formula A. Then, viscosity at T_(m) wasestimated from these parameters.

In(η/η₀)=−[A(T−T ₀)]/[B+(T−T ₀)]  [Formula A]

[0160] wherein, In represents natural logarithm, T represents absolutetemperature (K), T₀ represents reference temperature (K), η representsviscosity of the resin composition at T (mPa s), η₀ represents viscosityof the resin composition at T₀ (mPa s), and A and B represent constantsthat are inherent to a liquid.

[0161] Dielectric Measurement

[0162] Curing of the resin composition was monitored by dielectricmeasurement. The dielectric measurement device was MDE-10 curing monitormanufactured by Holometrix-Micromet. The TMS-1 inch sensor was installedin the lower plate of the programmable mini-press MP2000. The O-ringmade of Viton, which had internal diameter of 31.7 mm and thickness of3.3 mm, was placed on the lower plate of the press, and the temperatureof the press was set for predetermined T. The epoxy resin compositionwas poured into the inside of the O-ring, and the press was closed.Change of ionic viscosity of the resin composition vs. time wasmonitored. The dielectric measurement was carried out at the frequenciesof 1, 10, 100, 1,000 and 10,000 Hz.

[0163] The cure index was calculated by the following formula D. Then, aratio t₉₀/t₁₀ (wherein, t₁₀: time required for the cure index to reach10%, t₉₀: time required for the cure index to reach 90%) was determined.

cureindex=[log(α)−log(α_(min))]/[log(α_(max))−log(α_(min))]×100  [Formula D]

[0164] wherein,

[0165] log: common logarithm

[0166] unit of cure index: %

[0167] α: ionic viscosity (Ωcm)

[0168] α_(min): minimum ionic viscosity (Ωcm)

[0169] α_(max): maximum ionic viscosity (Ωcm)

[0170] Measurement of Glass Transition Temperature of a Cured ResinProduct

[0171] The O-ring made of Viton, which had internal diameter of 31.7 mmand thickness of 3.3 mm, was installed at the lower plate of theprogrammable mini-press MP2000, and the temperature of the press was setfor predetermined T. And then, the resin composition was added to theinterior of the O-ring, and the press was closed. The resin compositionwas cured for the predetermined period. The resulting cured resinproduct was cut to make a sample having a width of 12 mm and length of40 mm. The sample was measured by the viscoelastometer ARES manufacturedby Rheometric Scientific with a rectangular torsion mode, and withtemperature raising rate of 20° C./min, and frequency of 1 Hz, todetermine a peak of Loss modulus G″. If the number of the peaks is two,a peak of lower temperature is selected. From the peak of Loss modulusG″, the glass transition temperature was determined.

[0172] Estimation of t_(v)

[0173] Glass transition temperatures of the cured resin after 6, 8, 10,12, 14 and 20 minutes at the predetermined temperature T were measuredaccording to the above method. The time necessary for the glasstransition temperature of the cured resin products to reach T (t_(v))was estimated by interpolation of these data.

[0174] Preparation of a Cured Resin Plate

[0175] Stainless steel spacers with a dimension of 150 mm×150 mm×2 mmwere installed at the lower plate of a press, and the temperature of thepress was set for the predetermined temperature T. And then, the resincomposition was added to the interior of the spacer, and the press wasclosed. After 20 minutes, the press was opened to obtain the cured resinplate.

[0176] Measurement of Flexural Modulus of a Cured Resin

[0177] A sample with width of 10 mm and length of 60 mm was made bycutting the above cured resin plate. Flexural modulus was measured withthe 3 points flexural test according to ISO 178. The test device usedwas the Tensilon 4201 manufactured by Instron Company. The crossheadspeed used was 2.5 mm/min, span space was 32 mm, and the temperatureduring measurement was 23° C.

[0178] Measurement of Tensile Elongation of a Cured Resin

[0179] Tensile elongation was measured by using the above cured resinplate according to ISO 527-2. The test device used was the Tensilon 4201manufactured by Instron Company. The temperature during measurement was23° C.

[0180] Measurement of Fiber Volume Fraction (Vf) of a Fiber-ReinforcedComposite Material

[0181] The fiber volume fraction (Vf) of a fiber-reinforced compositematerial was measured according to ASTM D 3171.

[0182] Measurement of Density (ρ_(c)) of a Fiber-Reinforced CompositeMaterial

[0183] Density ρ_(c) of a fiber-reinforced composite material wasmeasured according to ASTM D 792.

[0184] Measurement of Glass Transition Temperature of a Fiber-ReinforcedComposite Material

[0185] The inlet side of the fiber-reinforced composite material was cutto make a sample with width of 12 mm and length of 55 mm. The sample wasmeasured by the viscoelastometer ARES manufactured by RheometricScientific with a rectangular torsion mode and with a temperatureraising rate of 20° C./min and frequency of 1 Hz, to determine the peakof Loss modulus G″. If there are two peaks detected, the peak of lowertemperature is selected. From the peak of Loss modulus G″, glasstransition temperature was determined.

[0186] Measurement of Specific Strength and Specific Elastic Modulus ofa Fiber-Reinforced Composite Material by Tensile Test

[0187] The fiber-reinforced composite material was cut to make a samplewith width of 12.7 mm and length of 229 mm, which had length directionidentical to the 0° direction. The 0° tensile strength σ (MPa) and 0°tensile modulus E (GPa) were measured with the sample according to ASTMD 3039. The test device used was the Tensilon 4208 manufactured byInstron Company. The crosshead speed was 1.27 mm/min, and thetemperature during measurement was 23° C. Specific strength (MPa cm³/g)and specific elastic modulus (GPa cm³/g) were determined by thefollowing formulas B and C and ρ_(c) measured in the above.

specific strength=σ/ρ_(c)  [Formula B]

specific elastic modulus=E/ρ _(c)  [Formula C]

[0188] Measurement of Density of a Core

[0189] Density of cores was measured according to ISO 845.

[0190] Measurement of Glass Transition Temperature of a Core

[0191] Glass transition temperature of core was measured using a samplewith width of 12 mm and length of 55 mm according to SACMA SRM18R-94.The test device used was the viscoelastmeter ARES manufactured byRheometric Scientific. The measurement was made with a rectangulartorsion mode, and with temperature raising rate of 5° C./min, andfrequency of 1 Hz, to determine storage modulus G′. From the onset ofthe storage modulus G′, glass transition temperature was determined.

[0192] Measurement of Shear Modulus of Elasticity of a Core

[0193] Shear modulus of elasticity of a core was measured using a samplewith width of 50 mm, length of 150 mm and thickness of 10 mm accordingto ASTM C 273.

[0194] Measurement of Surface Roughness R_(a) of a Fiber-ReinforcedComposite Material

[0195] Surface roughness R_(a) of a fiber-reinforced composite materialwas measured according to ISO 845. The test device used was Surftest 301manufactured by Mitutoyo.

Examples 1, 2, 3 and 5

[0196] The component (b) represented in Table 1, below, was added to thecomponent (c). This mixture was heated to 90° C. to make a solution. Theresulting solution was maintained at 70° C. The component (a) that hadbeen heated to 70° C. was added to the solution. The solution wasstirred for 1 minute to give an epoxy resin composition. The epoxy resincomposition of example 1 was turbid to white at 70° C. but became auniform solution at 100° C. The epoxy resin compositions of examples 2,3 and 5 were uniform solutions at 70° C.

[0197] The t₉₀/t₁₀ of the epoxy resin compositions of examples 1, 2, 3and 5 were 1.7, 1.8, 1.9 and 2.3, respectively, which were allsatisfactory values (FIG. 1 shows change of cure index of the resincompositions of examples 1 and 2 vs. time by dielectric measurement).

[0198] The t_(v)/t₁₀ of the epoxy resin compositions of examples 1, 2, 3and 5 were 1.9, 2.3, 2.5 and 1.9, respectively, which were allsatisfactory values.

[0199] The flexural modulus the cured resin products of examples 1, 2, 3and 5 were 3.5 GPa, 3.2 GPa, 3.1 GPa, and 3.4 GPa, respectively. Thetensile elongation of the cured resin products of examples 1, 2, 3 and 5were 4.1%, 4.7%, 4.8% and 4.5% respectively. These values weresufficiently high.

Example 4

[0200] The component (b) represented in Table 1 was added to thecomponent (c). This mixture was heated to 90° C. to make a solution. Theresulting solution was maintained at 70° C. The component (a) which hadbeen heated to 70° C. was added to the solution. The solution wasstirred for 1 minute to give an epoxy resin composition. The epoxy resincomposition was a uniform solution at 70° C.

[0201] The t₉₀/t₁₀ was 2.2, which was a satisfactory value.

[0202] The t_(v)/t₁₀ was 2.9, which was a relatively satisfactory value.

[0203] The flexural modulus of the cured resin product was 3.0 GPa,which was a relatively high value. The tensile elongation of the curedresin product was 4.4%, which was a sufficiently high value.

Examples 6 and 7

[0204] The component (b) represented in Table 1 was added to thecomponent (c). This mixture was heated to 90° C. to make a solution. Theresulting solution was maintained at 70° C. The component (a) which hadbeen heated to 70° C. was added to the solution. The solution wasstirred for 1 minute to give an epoxy resin composition. The epoxy resincompositions of examples 6 and 7 were uniform solutions at 70° C.

[0205] The t₉₀/t₁₀ of the epoxy resin compositions of examples 6 and 7were all 2.1, which were satisfactory values. The t_(v)/t₁₀ of the epoxyresin compositions of examples 6 and 7 were 2.4 and 2.5, respectively,which were satisfactory values.

[0206] The flexural modulus of the cured resin products of examples 6and 7 were 32 GPa and 31 GPa, respectively. The tensile elongation ofthe cured resin products of examples 6 and 7 were 4.3% and 4.0%. Thesevalues were sufficiently high.

Comparative Example 1

[0207] The component (b) represented in Table 1 was grinded with anagate mortar to give fine particulates. This was added to the component(a) that had been heated to 70° C. The mixture was stirred and dispersedfor 1 minute to give an epoxy resin composition. The epoxy resincomposition became a uniform solution at 100° C.

[0208] The t₁₀ of the epoxy resin composition was equal to those ofexamples 1 and 2. The t₉₀/t₁₀, however, was 3.6, which was not asatisfactory value (FIG. 1 shows change of cure index of the resincomposition vs. time by dielectric measurement).

[0209] The t_(v)/t₁₀ was 3.9, which was not a satisfactory value.

[0210] The flexural modulus of the cured resin product was 3.1 GPa,which was sufficiently high value, but the tensile elongation of thecured resin product was 1.7%, which was not a satisfactory value.

Comparative Example 2

[0211] The component (c) that had been heated to 70° C. was added to thecomponent (a) represented in Table 1. This was stirred for 1 minute togive an epoxy resin composition. Dielectric measurement showed thatthere was little change in the ion viscosity. The epoxy resincomposition of comparative example 2 was still liquid when observed byopening a programmable mini-press after 30 minutes.

Comparative Example 3

[0212] The component (b) represented in Table 1 was added to thecomponent (c). This mixture was heated to 90° C. to make a solution. Theresulting solution was maintained at 70° C. The component (a) that hadbeen heated to 70° C. was added to the solution. The solution wasstirred for 1 minute to give an epoxy resin composition. The epoxy resincomposition was turbid to white, even at 100° C.

[0213] In the dielectric measurement, the α_(max) could not be measuredbecause ion viscosity changed too slowly.

[0214] Also, t_(v) could not be estimated because the glass transitiontemperature of the epoxy resin composition was only 52° C. after 20minutes.

Example 8

[0215] A monolithic plate of fiber-reinforced composite material wasprepared by using the epoxy resin composition of example 5 at the moldtemperature of 90° C.

[0216] The initial viscosity of the epoxy resin composition of example 5at 90° C., which was estimated by the formula WLF, was 36 mPa s.

[0217] Referring to FIG. 2, the mold used comprised a rectangularparallelepiped cavity with a width of 600 mm, length 600 mm and height1.5 mm (reference number 1), upper mold (reference number 2), and lowermold (reference number 3), wherein the upper mold had an inlet(reference number 4) and outlet (reference number 5), the lower mold hadrunners and film gates (reference numbers 8 and 9) corresponding to theinlet and the outlet (reference numbers 6 and 7).

[0218] For reinforcing fiber substrates, a 600 mm×600 mm square carbonfiber fabrics C06343 (using T300B-3K, areal weight 192 g/m², Toray Co.,Ltd.), which had sides parallel to weft and warp of the carbon fiberfabrics, was used. For a peel ply, a 600 mm×600 mm square polyesterfabric was used. For resin distribution medium, 580 mm×580 mm squarenylon net was used.

[0219] Referring to FIG. 3, after six reinforcing fiber substrates(reference number 10), a peel ply (reference number 11) and a resindistribution medium (reference number 12) were placed in the cavity ofthe mold, and the mold was closed. The pressure of the inside of themold that was maintained at 98° C. decreased to atmospheric pressure−0.1 MPa with a vacuum pump connected to the outlet. The epoxy resincomposition of example 5 was injected into the mold with an injectionpressure of 0.2 MPa. The injection was terminated after 6.5 minutes fromthe beginning of injection. The mold was opened after 25 minutes fromthe beginning of injection, and a fiber-reinforced composite materialwas obtained.

[0220] The Vf of the fiber-reinforced composite material was 52%.

[0221] The glass transition temperature of the fiber-reinforcedcomposite material was 98° C.

[0222] The specific strength and specific elastic modulus of thefiber-reinforced composite material were 400 MPa cm³/g and 40 GPa cm³/g,which were sufficiently high values.

[0223] The surface roughness R_(a) of the fiber-reinforced compositematerial was 0.38 μm, which was a satisfactory value.

Example 9

[0224] A monolithic plate of fiber-reinforced composite material wasprepared by using the epoxy resin composition of example 5 at the moldtemperature of 105° C. The initial viscosity of the epoxy resincomposition of example 5 at 105° C., which was estimated by the formulaWLF, was 20 mPa s.

[0225] The mold used, reinforcing fiber substrates, a peel ply and aresin distribution medium were all the same as those of example 8.Referring to FIG. 3, after six reinforcing fiber substrates (referencenumber 10), a peel ply (reference number 11) and a resin distributionmedium (reference number 12) were placed in the cavity of the mold, andthe mold was closed. The pressure of the inside of the mold that wasmaintained at 105° C. was decreased to atmospheric pressure −0.1 MPawith a vacuum pump connected to the outlet. The epoxy resin compositionof example 5 was injected into the mold with an injection pressure of0.2 MPa. The injection was terminated after 3.3 minutes from thebeginning of injection. The mold was opened after 12.0 minutes from thebeginning of injection, and a fiber-reinforced composite material wasobtained.

[0226] The Vf of the fiber-reinforced composite material was 52%.

[0227] The glass transition temperature of the fiber-reinforcedcomposite material was 116° C.

[0228] The specific strength and specific elastic modulus of thefiber-reinforced composite material were 380 MPa cm³/g and 40 GPa cm³/g,which were sufficiently high values.

[0229] The surface roughness R_(a) of the fiber-reinforced compositematerial was 0.44 μm, which was a satisfactory value.

Example 10

[0230] A monolithic plate fiber-reinforced composite material wasprepared by using the epoxy resin composition of comparative example 1at the mold temperature of 105° C.

[0231] The mold used, reinforcing fiber substrates, a peel ply and aresin distribution medium were the same as those of example 8. Referringto FIG. 3, after six reinforcing fiber substrates (reference number 10),a peel ply (reference number 11) and a resin distribution medium(reference number 12) were placed in the cavity of the mold, and themold was closed. The pressure of the inside of the mold that wasmaintained at 105° C. decreased to atmospheric pressure −0.1 MPa with avacuum pump connected to the outlet. The epoxy resin composition ofcomparative example 1 was injected into the mold with an injectionpressure of 0.2 MPa. The injection was terminated after 2.8 minutes fromthe beginning of injection. The mold was opened after 12.0 minutes fromthe beginning of injection, and a fiber-reinforced composite materialwas obtained.

[0232] The glass transition temperature of the fiber-reinforcedcomposite material was 88° C., which was very much lower than the moldtemperature.

Example 11

[0233] A fiber-reinforced composite material of sandwich structure wasprepared by using the epoxy resin composition of example 5 at the moldtemperature of 90° C.

[0234] Referring to FIG. 2, the mold used comprised a rectangularparallelepiped cavity with a width of 600 mm, length 600 mm and height13.5 mm (reference number 1), upper mold (reference number 2), and lowermold (reference number 3), wherein the upper mold had an inlet(reference number 4) and outlet (reference number 5), the lower mold hadrunners and film gates (reference numbers 8 and 9) corresponding to theinlet and the outlet (reference numbers 6 and 7).

[0235] For the reinforcing fiber substrates, rectangular (width 600 mm,length 598 mm) carbon fiber fabrics C06343 (using T300B-3K, areal weight192 g/m², Toray Co., Ltd.) of which sides are parallel to weft and warpof the carbon fiber fabrics were used.

[0236] For the core, Rohacell 511G which had a thickness of 12.7manufactured by Rohm Company was used, which was cut to width of 600 mmand length of 598 mm, and on which resin distribution grooves with across section of rectangle with width of 1 mm and depth of 2 mm areengraved longitudinally parallel to one another with intervals of 25 mmon the upper and the lower surfaces. The density, the glass transitiontemperature, and the shear modulus of the Rohacell 511G were 0.052g/cm³, 152° C., and 19 MPa.

[0237] Referring to FIG. 4, after two reinforcing fiber substrates(reference number 15), a core (reference number 13) having resindistribution grooves (reference number 14) and two reinforcing fibersubstrates (reference number 15) were overlapped over one another in thecavity of the mold, and the mold was closed. The reinforcing fibersubstrates and the core were placed in a manner such that gaps of 1 mmwidth were formed beside the inlet and the outlet, and nylon nets wereset to the gaps to introduce the resin composition into the resindistribution grooves at the lower surface of the core. Then, thepressure of the inside of the mold that was maintained at 90° C. wasdecreased to atmospheric pressure −0.1 MPa with a vacuum pump connectedto the outlet. The epoxy resin composition of example 5 was injectedinto the mold with an injection pressure of 0.2 MPa. The injection wasterminated after 4.8 minutes from the beginning of injection. The moldwas opened after 20.0 minutes from the beginning of injection, and afiber-reinforced composite material was obtained.

[0238] The surface roughness R_(a) of the fiber-reinforced compositematerial was 0.39 μm, which was satisfactory value.

Example 12

[0239] A sandwich structure fiber-reinforced composite material wasprepared by using the epoxy resin composition of example 5 at the moldtemperature of 105° C.

[0240] The mold used, reinforcing fiber substrates and a core were thesame as those of example 11.

[0241] Referring to FIG. 4, after two reinforcing fiber substrates(reference number 15), a core (reference number 13) having resindistribution grooves (reference number 14) and two reinforcing fibersubstrates (reference number 15) were overlapped over one another in thecavity of the mold, and the mold was closed. The reinforcing fibersubstrates and the core were placed in a manner such that gaps of 1 mmwidth were formed beside the inlet and the outlet of the cavity, andnylon nets were set to the gaps to introduce the resin composition intothe resin distribution grooves at the lower surface of the core. Thepressure of the inside of the mold that was maintained at 105° C. wasdecreased to atmospheric pressure −0.1 MPa with a vacuum pump connectedto the outlet. The epoxy resin composition of example 5 was injectedinto the mold with an injection pressure of 0.2 MPa. The injection wasterminated after 2.2 minutes from the beginning of injection. The moldwas opened after 10.0 minutes from the beginning of injection, and afiber-reinforced composite material was obtained.

[0242] The surface roughness R_(a) of the fiber-reinforced compositematerial was 0.45 μm, which was a satisfactory value.

INDUSTRIAL APPLICABILITY

[0243] According to the present invention, a high Vf fiber-reinforcedcomposite material will be made by the RTM method with goodproductivity.

[0244] The epoxy resin composition of the present invention has thecharacteristic of long injectable time and short curing time. Therefore,a high Vf fiber-reinforced composite material will be produced with goodproductivity by using the epoxy resin composition of the presentinvention.

[0245] Because the fiber-reinforced composite materials produced by theprocess of the present invention or the fiber-reinforced compositematerials obtained from the epoxy resin composition of the presentinvention have good mechanical properties such as strength and elasticmodulus, they are preferably used for structural parts, outer skins andaerodymamic parts of transports, such as spacecrafts including rockets,artificial satellites, and the like, aircrafts, trains, marines,automobiles, motorcycles, bicycles, and the like. Among them, they areparticularly preferably used for structural parts, outer skins andaerodymamic parts of motorcycles and automobiles produced in massquantities. TABLE 1 Comparative Examples examples 1 2 3 4 5 6 7 1 2 3composition of epoxy component a “Epo-Tohto” YD128 100 100 100 100 100100 100 100 100 100 resin (% by weight) (di-functional aromatic epoxyresin) component b 2-methylimidazole 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 —3.0 (imidazole derivative) component c glycerin (alcohol) 3.1 — — — — —— — 3.1 4.0 1,2-ethandiol (alcohol) — 2.1 — — — — — — — — benzyl alcohol— — 3.6 — — — — — — — (alcohol) isopropyl alcohol — — — 2.1 — — — — — —(alcohol) propylene glycol) — — — — 2.0 — — — — — (alcohol) “Rikaresin”PO-20 — — — — 6.0 — — — — — (alcohol) 2,4-dimethylphenol — — — — — 4.1 —— — — (phenol) propionic acid — — — — — — 2.5 — — — (carboxylic acid)viscosity of the component (a) at 25° C. (Pa s) 12.0 12.0 12.0 12.0 12.012.0 12.0 12.0 12.0 12.0 initial viscosity of the epoxy resincomposition at 25° C. (Pa s) 12.3 11.9 6.3 6.9 8.7 8.7 10.6 13.4 12.827.8 curing properties of the temperature T (° C.) 100 100 100 100 100100 100 100 100 100 epoxy resin composition t₁₀ (min.) 3.5 3.3 3.2 3.83.8 3.1 4.2 3.2 — — t₉₀ (min.) 6.0 6.1 6.2 8.2 8.9 6.4 8.8 11.5 — —t₉₀/t₁₀ 1.7 1.8 1.9 2.2 2.3 2.1 2.1 3.6 — — glass transition temperature94 85 86 — 95 89 — — — — after 6 minutes at T (° C.) glass transitiontemperature 115 105 103 88 111 106 84 68 — — after 8 minutes at T (° C.)glass transition temperature 117 110 109 96 118 113 99 85 — — after 10minutes at T (° C.) glass transition temperature 120 113 112 104 120 115103 98 — — after 12 minutes at T (° C.) glass transition temperature 121115 114 108 122 118 107 106 — — after 14 minutes at T (° C.) glasstransition temperature 124 116 116 112 125 121 113 115 — 52 after 20minutes at T (° C.) t_(v) (min.) 6.6 7.5 8.0 11.0 7.3 7.3 10.5 12.5 — —t_(v)/t₁₀ 1.9 2.3 2.5 2.9 1.9 2.4 2.5 3.9 — — physical properties offlexural modulus of elasticity (GPa) 3.5 3.2 3.1 3.0 3.4 3.2 3.1 3.1 — —the cured resin product tensile elongation (%) 4.1 4.7 4.8 4.4 4.5 4.34.0 1.7 — —

[0246] TABLE 2 Examples 8 9 10 molding mold temperature 90 105 105condition T_(m)(° C.) t_(i) (min.) 6.5 3.3 2.8 t_(m) (min.) 25.0 12.012.0 t_(m)/t_(i) 3.8 3.6 4.3 viscosity 10° C. 154500 154500 391000 ofthe 30° C. 3930 3930 13350 resin 50° C. 439 439 922 composition 70° C.102 102 112 (mPa s) viscosity at T_(m) 36 20 9 estimated by the formulaWLF physical degree of impregnation overall overall overall propertiesVf (%) 52 52 — of the Density ñ_(c) (g/cm³) 1.5 1.5 — composite glasstransition temp- 98 116 88 material erature after t_(m) (° C.) specificstrength by 400 380 — tensile test (MPa · cm³/g) specific elastic 40 40— modulus by tensile test (GPa · cm³/g) surface roughness R_(a) 0.380.44 — (μm)

[0247] TABLE 3 Examples 11 12 molding mold temperature T_(m) (° C.) 90105 condition t_(i) (min.) 4.8 2.2 t_(m) (min.) 20.0 10.0 t_(m)/t_(i)4.2 4.5 viscosity of the 10° C. 154500 154500 resin composi- 30° C. 39303930 tion (mPa s) 50° C. 439 439 70° C. 102 102 viscosity at T_(m)estimated 36 20 by the formula WLF physical Density ñ_(c) (g/cm³) 0.0520.052 properties of glass transition temperature 152 152 core member (°C.) shear modulus of elasticity 19 19 (MPa) surface degree of surfaceroughness R_(a) (μm) 0.39 0.45 the composite material

What is claimed is:
 1. An epoxy resin composition, comprising: component(a) epoxy resin, component (b) anionic polymerization initiator andcomponent (c) proton donor, wherein the amount of component (c) based on100 parts by weight of component (a) is 1 to 30 parts by weight;component (a) is a liquid; and components (b) and (c) are homogeneouslydissolved in component (a).
 2. The epoxy resin composition according toclaim 1, wherein said component (b) is a tertiary amine.
 3. The epoxyresin composition according to claim 2, wherein said component (b) is animidazole derivative.
 4. The epoxy resin composition according to claim3, wherein said component (b) is represented by the following generalformula I:

wherein, R¹ represents a member selected from the group consisting ofhydrogen atom, a methyl group, an ethyl group, a benzyl group and acyanoethyl group; R², R³ and R⁴ independently one on other represent amember selected from the group consisting of hydrogen atom, a methylgroup and an ethyl group.
 5. The epoxy resin composition according toclaim 1, wherein said component (c) is at least one member selected fromthe group consisting of an alcohol, a phenol, a mercaptan, a carboxylicacid and a 1,3-dicarbonyl compound.
 6. The epoxy resin compositionaccording to claim 5, wherein said component (c) is a compound havingtwo or more active hydrogen in one molecule.
 7. The epoxy resincomposition according to claim 5, wherein said component (c) has onemember selected from the group consisting of an aromatic ring, acycloalkane ring and a cycloalkene ring.
 8. The epoxy resin compositionaccording to claim 5, wherein said component (c) is an alcohol.
 9. Theepoxy resin composition according to claim 8, wherein said component (c)is an alcohol which has a boiling point of greater than 100° C. atatmospheric pressure.
 10. The epoxy resin composition according to claim1, wherein the initial viscosity of the composition at 25° C. is between1 to 30,000 mPa s.
 11. The epoxy resin composition according to claim 1,wherein the epoxy resin composition satisfies the following conditions(1) to (3) at a specific temperature T that is between 60 to 180° C.:1≦t₁₀≦10  (1) 3≦t₉₀≦30  (2) 1<t ₉₀ /t ₁₀≦3  (3) wherein, t₁₀ is time (inminutes) required for the cure index to reach 10% from the beginning ofthe measurement, which is determined by dielectric measurement at thetemperature T and t₉₀ is time (in minutes) required for the cure indexto reach 90% from the beginning of the measurement, which is determinedby dielectric measurement at the temperature T.
 12. The epoxy resincomposition according to claim 1, wherein the epoxy resin compositionsatisfies the following conditions (4) to (6) at a specific temperatureT that is between 60 to 180° C.: 1≦t₁₀≦10  (4) 3≦t_(v)≦30  (5) 1<t _(v)/t ₁₀≦3  (6) wherein, t₁₀ is time required for the cure index to reach10% from the beginning of the measurement, which is determined bydielectric measurement at the temperature T(min.) and t_(v) is time (inminutes) required for the glass transition temperature of the curedresin product to reach T from the beginning of the measurement at thetemperature T
 13. A method of producing a fiber-reinforced compositematerial by injecting the epoxy resin composition of claim 1 intoreinforcing fiber substrates placed in a mold and curing by heat.
 14. Amethod of producing a fiber-reinforced composite material by injecting athermosetting resin composition into reinforcing fiber substrates placedin a mold maintained at a specific temperature T_(m) between 60 to 180°C. and curing by maintaing the mold temperature at Tm, which satisfy thefollowing conditions (7) to (9): t_(i)≦10  (7) t_(m)≦60  (8) 1<t _(m) /t_(i)≦6.0  (9) wherein, t_(i) is time (in minutes) from the beginning ofthe injection to the termination of the injection and t_(m) is time (inminutes) from the beginning of the injection to the beginning ofdemolding (min.)
 15. The method of producing a fiber-reinforcedcomposite material according to claim 14, wherein the initial viscosityof the thermosetting resin composition at T_(m) calculated by theformula WLF is between 0.1 to 300 mPa s.
 16. The method of producing afiber-reinforced composite material according to claim 14, wherein theglass transition temperature of the fiber-reinforced composite materialafter t_(m) from the beginning of the injection is more than T_(m)−15°C.
 17. The method of producing fiber-reinforced composite materialaccording to claim 14, wherein said reinforcing fibers are carbonfibers.
 18. The method of producing a fiber-reinforced compositematerial according to claim 14, wherein the fiber volume fraction isbetween 40 to 85%.
 19. The method of producing fiber-reinforcedcomposite material according to claim 14, wherein the fiber volumefraction is between 45 to 85%.
 20. The method of producing afiber-reinforced composite material according to claim 14, wherein aresin distribution medium is used.
 21. The method of producing afiber-reinforced composite material according to claim 14, wherein amold having resin distribution grooves is used.
 22. The process forproducing fiber-reinforced composite material according to claim 14,wherein a core having resin distribution grooves is used.
 23. A curedproduct of the epoxy resin composition of claim
 1. 24. Afiber-reinforced composite material consisting of the cured product ofclaim 23 and reinforcing fibers.
 25. The fiber-reinforced compositematerial according to claim 24, wherein said reinforcing fibers arecarbon fibers.
 26. The fiber-reinforced composite material according toclaim 24, wherein the fiber volume fraction is between 40 to 85%. 27.The fiber-reinforced composite material according to claim 24, whereinthe fiber volume fraction is between 45 to 85%.
 28. A fiber-reinforcedcomposite material produced by the method of claim
 14. 29. Thefiber-reinforced composite material according to claim 24, wherein thespecific strength of the fiber-reinforced composite material is morethan 250 MPa cm³/g.
 30. The fiber-reinforced composite materialaccording to claim 28, wherein the specific strength of thefiber-reinforced composite material is more than 250 MPa cm³/g.
 31. Thefiber-reinforced composite material according to claim 24, wherein thespecific elastic modulus is more than 28 GPa cm³/g.
 32. Thefiber-reinforced composite material according to claim 28, wherein thespecific elastic modulus is more than 28 GPa cm³/g.
 33. Afiber-reinforced composite material having a sandwich structure whichhas a skin comprised of the fiber-reinforced composite material of claim24.
 34. A fiber-reinforced composite material having a sandwichstructure produced by the process of claim
 14. 35. The fiber-reinforcedcomposite material according to claim 33, wherein density of the coremember is between 0.02 to 0.10 g/cm³.
 36. The fiber-reinforced compositematerial according to claim 34, wherein density of the core member isbetween 0.02 to 0.10 g/cm³.
 37. The fiber-reinforced composite materialaccording to claim 33, wherein glass transition temperature of the coremember is more than 80° C.
 38. The fiber-reinforced composite materialaccording to claim 34, wherein glass transition temperature of the coremember is more than 80° C.
 39. The fiber-reinforced composite materialaccording to claim 24, wherein surface roughness R_(a) of at least oneside of the fiber-reinforced composite material is less than 1.0 μm. 40.The fiber-reinforced composite material according to claim 28, whereinsurface roughness R_(a) of at least one side of the fiber-reinforcedcomposite material is less than 1.0 μm.
 41. A structural member for anautomobile comprising the fiber-reinforced composite material of claim24.
 42. A structural member for an automobile comprising thefiber-reinforced composite material of claim
 28. 43. An outer plate ofan automobile comprising the fiber-reinforced composite material ofclaim
 24. 44. An outer plate of an automobile comprising thefiber-reinforced composite material of claim
 28. 45. An aerodynamic partfor an automobile comprising the fiber-reinforced composite material ofclaim
 24. 46. An aerodynamic part for an automobile comprising thefiber-reinforced composite material of claim 28.